Method of temporarily plugging openings in well casing and apparatus therefor



United States METHOD F TEMPGRARHLY PLUGGING OPEN- INGS IN WELL CASNG AND APPARATUS THEREFOR Solis Myron Zandmer, Banff, Alberta, Canada, and Lyle Caldwell, Los Angeles, and John B. Goodwin, Lyn- .wood, Calif.; said Goodwin assigner of one-half to said Zandmer, and one-half to said Caidwell Filed Dec. 22, 1958, Ser. No. 782,935 14 Claims. (Cl. 166-21) The present invention relates generally to wells and bore holes in the earth, for example, oil wells, and more especially to method and apparatus for temporarily plugging openings in a casing or the like set in a well. The operation of plugging the openings may be carried out in conjunction with or as part of a procedure for treating the surrounding formations in order to increase oil production, or for other purposes. Since the invention is particularly adapted to use for this purpose in oil wells, it will be so described.

After a well has been drilled to the desired depth and passes through an oil producing formation, it is common practice to set casing in the well by surrounding the casing with cement. It has then been common practice to perforate the casing and the surrounding cement at the level of the producing formation, by any suitable method. The oil and `gas leaving the producing formation can then pass through the openings in the casing and rise within the well to reach the surface of the ground. ln order to increase the rate of production of gas and oil, various types of treatment have been applied to the formations, such as acidizing, fracturing and so on.

In general, all of these treating processes require the application of fluids to the formation under more or less high pressures Vto lforce the fluid into the pore spaces, small cracks, and crevices of the formation. To enable development of the required high uid pressures, it is preferable to plug some of the openings in the casing in a temporary manner, leaving other openings through which iiuid under pressure can be forced out of the casing. The plugs used are temporary and they are removed from the openings after the treatment in order again to admit oil and gas into the casing.

One method of introducing plugging elements into an oil well is that ydisclosed in U.S. Patent No. 2,754,910 issued July 17, 1956, to Derrick et al. According to the patent, the plugging elements are introduced at ground level into the stream of fluid being pumped down the well.

'These plugging elements are carried with the iluid down the well and lodge in the openings through which fluid iiows out of the casing.

This method has certain disadvantages which make it a relatively slow process to plug a desired number of openings. The balls used as plugging elements must travel with the fluid stream from the ground level for along distance, usually several thousand `feet, to the point where the openings to be plugged are located. The time of travel is substantial and a relatively large volume of iiuid must be pumped down the well and then into the formation in order to carry the plugging elements to the desired location. These considerations are particularly important if a given number of balls added to the fluid stream are found to be inadequate and it then becomes necessary to add more of them. All of these features combine to make the known method very time consuming and therefore very expensive.

It is therefore a general object of our invention to provide a novel method of introducing plugging elements into casing -in a bore hole that will permit the operation to be carried out with a minimum of time.

Another object of our invention is to shorten to a miniice mum the length of the path from the point of release of the plugging elements to the location at which the lodge in the openings in the casing.

A further object of the invention is to enable the operator to maintain a maximum degree of control over the operation of plugging the casing openings and to introduce the plugging elements singly at time intervals as desired.

These objects of our invention have been achieved in our novel method of plugging openings in the casing in a well and includes the steps of lowering a plurality of plugging elements as a group into the casing to a position in the vicinity of the openings, introducing at the ground level fluid under pressure into the Well, thus causing fluid to ow outwardly through these openings, and releasing one or more ofthe plugging elements from the group into the fluid stream each to be carried by the uid stream to one of the openings to be plugged. Release of successive plugging elements is effected by a series of control impulses generated at the ground surface and transmitted through the iiuid column in the well to actuate the release mechanism.

In a preferred form of apparatus -for carrying out our improved method we provide a magazine, holding a plurality of plugging elements, which is adapted to be lowered down the well within the casing and is open at its lower end to the space within the casing, gate means at the lower end of the magazine to control the passage of plugging elements from the magazine into said well space, and gate operating means operable in response to controlled conditions existing in the fluid body, as for example a pressure differential, rate of fluid flow, and so on.

How the above objects and advantages of our invention are achieved will be more readily understood by reference to the following description and to the annexed drawing, in which:

FlG. 1 is a vertical section through a bore hole showing -diagrammatically 4a perforated casing cemented in a well.

FIG. 2 is an enlarged vertical section through a preferred form of magazine and ball release means.

FIG. 3 is a fragmentary bottom plan as indicated by line 3-3 of FIG. 2.

FIG. 4 is a fragmentary vertical section showing a variational form of gate and gate operating means for releasing plugging elements.

Our novel method of plugging openings in the casing involves lowering a plurality of plugging elements into the well as a group in a suitable container or magazine. The usual tubing may be used for the purpose of lowering the elements. The elements are then released at will into the fluid stream, preferably one at =a time but more may be released at once. The iluid stream carries them to the openings where they lodge and are held by fluid pressure. Release of the elements is effected from the ground surface by transmitting through the fluid a control impulse that actuates the release means. Since the method is most easily understood from a description of suitable mechanism for practising the method, such mechanism will now be described.

Referring to the drawing there is shown in FIG. l at 10 a bore hole extending from the surface of the ground down to oil producing strata v11. Within the bore hole is casing 12, the lower end tof which is surrounded by a body 14 of cement. A plurality of passages or openings 16 extend outwardly through 'the casing wall and the surrounding cement to eifect communication between producing `strata 11 land the space 12a inside casing 12. Openings 16 may be produced by any `suitable means and they are here shown diagrammatically; but one preferred means for providing these openings is illustrated in Zandmer Patent No. 2,775,304 issued December 25, 1956. The `apparatus disclosed therein for providing openings through the casing to the producing formation results in a smooth circular seat at the inner end of each opening which makes it easily possible to obtain a substantially fluid tight closure of the opening by means lof the plugging elements later described. Other means of perfora'ting the casing, such as bullets, may be used to produce openings in the casing.

Casing 12 extends to the top of the well where it is connected by pipe 18 to pump 19 which is adapted to pump a suitable fluid under pressure down either the casing 12 or -the tubing 20 which is inside casing 12 and of smaller diameter to leave Ian annular space 21 between it and the inner wall of the casing. The tubing extends to the top of the ground and provides a conduit through which oil and/or gas may be removed from the well. Near its lower end, tubing 20 carries packer 22 which seals olf the annular space 21 between the tubing and the casing in order lto permit development of the necessary high pressure on fluid within the tubing and in the casing space 12a at the bottcrm of the well.

Connected to the lower end of tubing 20 below packer 22 is our novel apparatus for releasing plugging elements into the well. A preferred form of this apparatus, designated generally at 23, is shown in greater detail in FIG. 2. It comprises a body 25 having a centrally located passage 26 extending through the body which opens at the lower end of the body to the space 12a inside casing l2. Suitably attached to body 25 and extending upwardly therefrom within tubing 26 is a hollow tube 27 forming a magazine adapted to hold a plurality of spherical plugging elements 28. The tube 27 is closed at its upper end by a removable cap and is open at its lower end. Tube 27 is in registration with passage 26 in body 25, so that passage 26 also constitutes part of the magazine. The removable cap is not illustrated as it is not an essential part of this invention but it may be a screw threaded cap or a cap of any other suitable type.

Plugging elements 28 are able to move downwardly within tube 27 and to fall by gravity out the open lower end of passage 26 when permitted to do .so by the position of gate 39 which is pivotally mounted by pin 31 on body 25. Gate 38 is adapted to oscillate through a short arc in a vertical plane, such movement being imparted to the gate by operating rod 32 pivotally connected at its lower end to the gate. The upper end of operating rod 32 is attached to follower 34 which is normally urged upwardly by the action of compression spring 35 which bears a-t its upper end against the bottom of follower 34 and is seated at its lower end against a shoulder on body 25.

Gate projects into passage 26, and the end in the passage is concave to provide two vertically spaced arms Bb and 30o adapted to engage the balls 28 alternately. In the raised position, arm 30e engages the lowermost ball to retain it and the balls above it in passage 26. When the gate -is lowered to position 30a, the upper arm 30b engages the ball next above the lowermost one to hold back -t-he column of balls. At this time the lowermost ball is released from the magazine to drop into the well. The wall of bore 26 may be relieved opposite gate 30 to facilitate release ofthe lowermost ball when the gate is lowered.

Above and engaged by follower 34 is ball check valve 38 which is normally urged by spring 35 and the follower into engagement with a valve seat on sleeve 39. Sleeve 39 -is hollow and open at both ends to communicate with the cavity containing follower 34, spring and gate 30. This cavity, indicated generally at 40 provides a fluid passage through body 25 from the upper end to the lower end. Fluid flow through the passage is normally prevented -by check valve 38 being closed but fluid may flow downwardly through the passage when the fluid pressure above valve 38 exceeds that below the valve by a predetermined amount.

In order to insure the full range tof travel of valve 38 and rod 32, valve 38 is preferably surrounded by sleeve 41. The sleeve reduces the area available for fluid to flow past ball 38; and at the restricted rate iluid exerts enough pressure on the valve to move rod 32 and gate 30 downward for the full range of desired travel. Without sleeve 41, rod 32 may not move far enough to operate gate 30;

One or more additional iluid passages 42, Similar to each other, are `also provided extending through body 25. Within each passage 42, as in the one passage shown in FIG. 2, is a check valve 43 normally urged against an annular seat on sleeve 44 by follower 45 and compression spring 46 which bears against the body and against the lower end of the follower to hold the valve closed. When check valve 43 is opened by an excess of lluid pres- .sure above the valve, fluid may ilow downwardly through passage 42 past the :open valve and out the open lower end of the passage into the well space 12a within casing 12 and below packer 22.

Having described the construction of a preferred form of apparatus for carrying out our improved method, we shall now describe how our method is carried out with the aid of this particular apparatus.

As a preliminary step, it is necessary to fll magazine 27 with a number of plugging elements 28. These elements are preferably made of a synthetic resin or plastic of a suitable nature. These elements are preferably spherical in shape because elements of this shape are always properly oriented to lodge effectively in an opening 16, the diameter of the lballs 28 being slightly larger than the openings to be closed. Typically the balls are about it "-1" in diameter. They are preferably made of a material having a density slightly greater than the lluid to be forced into the surrounding formation. The lluid is water plus various additives or compounds. For example, if the formation is to be given an acid treatment, the usual acid lluid has a density in the vicinity of 1.05-1.08. In this case the density of the `balls is preferably about 1.1. Fluids used for other treatments may have higher or lower densities but ordinarily the density of the plugging elements is preferred to be about 3 and not more than 5% greater than the density of the fluid. Hence the density of these balls usually lies in the range of 1.05 to 1.15.

First, magazine 27 is filled with balls 28. Some of them fall down to fill passage 26 in the body. This en- Itire assembly is then attached to the lower end of tubing 20 in any suitable way with magazine 27 extending upwardly inside the tubing 20. Clearance between the tubing and magazine is sulllcient to permit flow of iluid past the magazine. The tubing with the ball release mechanism 23 on the lower end and with a packer 22 above the ball release mechanism is then lowered inside the Well casing in the usual manner until the ball release mechanism is in the vicinity of ybut preferably above openings 16 which are to be plugged. Actually the ball release Imechanism may be or 200 feet or more above the openings 16 vbut it will be realized that the balls are now located relatively close to the openings 16 compared with the several thousand `feet that these openings are below the earths surface. In other words, even though balls 28 travel 100 or 200 feet, or even more, from release mechanism 23 to reach holes 16, this is but a small fraction of Ithe travel required had they been introduced into the fluid stream at the ground surface.

The next operati-on is to expand packer 22 in order to confine liquid under pressure below it. This operation, as well as the construction of the packer, is well known in the oil well art and needs no detailed explanation here.

To release balls 28 into the fluid streams, pump 19 is started, building up pressure on the fluid Within tubing 20 and above valve 38 and 43. When the pressure differential between the rupper and lower sides of valve 38 reaches a predetermined value, for example p.s.i., the valve 38 opens allowing liquid to flow through passage 40. The downward movement of valve 38 and follower 34 moves gate 30 from its normal upper position, shown in full lines in FIG. 2, to the lower position 30a shown in broken lines. This movement of the gate permits the lowermost ball 2'8 to drop out the open end of passage 26 into the iluid stream to be carried by the flow of fluid to seat in an opening 16. Arm 30h on the gate engages the next ball to hold back the other balls. The ilow of uid through passage 40 is relatively restricted by sleeve 41; and by increasing the speed of pump 19 fluid pressure above valves 38 and 43 can be further increased. At some pressure above the pressure at which valve B8 opened, `for example about 125 p.s.i. higher, valve 43 opens in response to the increased pressure diierential. This allows liiuid to iiow through passage or passages 42 also, admitting fluid at a greater ilow rate into space 12u below packer 22.

Additional balls 2S may be released one at a time by varying the speed of pump 19 -in such a manner that the fluid pressure above valve 38 is raised and lowered sufficiently to cause the valve to open and close. With each cycle of movement of the valve gate 30 is actuated to release one of the plugging elements 28. While it is preferred to release only one ball 218 at a time to retain maximum control over the operation, gate means can be designed to release more than one ball on each cycle of operation. If pressure is reduced above the valves 43 and 38 they close when the reduction is equal to or greater than the differential pressures Imentioned above as required to open them. Acting as check valves, they maintain the full operating pressure on iiuid in the casing below packer 22. Hence it is not necessary to reduce the pump pressure to zero to operate the ball releasing means.

As a part of the procedure of treating formations, iluid may be pumped down the casing and outside the tubing prior -to setting the packer. This increases pressure in space 12a, closing valves 43 and 3'8 to prevent reverse ow up tubing 20.

Pressure Within the lluid is only one characteristic or condition existing within the fluid in the tubing that may be used according to our method to actuate the mechanism for releasing plugging elements. Other characteristics available for use include Ithe rate of iluid ow and also the volume of fluid passing a given location. These characteristics can be controlled by the speed of pump 19, since as the pump speed changes, the rate of -tlow down tubing 20 changes correspondingly. Of course when using the rate of iiow or Volume of iiuid the mechanism for releasing plugging elements is changed accordingly to respond to the dierent condition in the fluid. iIn case volume of flu-id is used, suitable metering means may be operated by fluid flow to release balls at timed intervals determined by the volume of fluid pumped through the ball release means.

These conditions are controlled by pump 19` located at the surface ofthe ground. The changes in conditions are therefore controlled from the ground surface. Broadly speaking, a change in pressure, iiow rate, .or both, within the wel-l may be regarded as an impulse or signal generated at the surface of the ground and transmitted through the liuid column in the tubing -to the ball release means to control the operation of the gate for releasing the balls into the well. Thus the method of our invention is considered to comprehend any manner of generating the control signal or impulse at the ground surface and transmitting it through the liquid body for this purpose.

A variational -form of apparatus for carrying out our invention is disclosed in FIG. 4. In this embodiment of the invention, gate 50 is pivotally mounted on body 25a by pin 51. On the opposite side of the pivot from plugging elements 28 is pivotally connected operating rod 53. Operating rod S3 is slidably mounted in guide bushing 55. The upper end of the rod 'acts as a piston which reciprocates vertically within cylinder 56 provided by a bore within bushing 55. Access yfor iiuid to the upper end of cylinder 56 is through inlet passage 58 and screen 59 covering the passage. Screen 59 is a very fine screen supported internally in a suitable manner to resist high external pressures and is `preferably furnished to prevent 6 abrasive particles in the fluid from entering the cylinder 56.

Operating rod 53 is normally urged upwardly to the position shown by compression spring 60 which bears against a pin 6'1 through rod 53 and an abutment 62 on body 25a. This upward force can be overcome by a downward force exerted by iluid under pressure against the upper end of piston 53, this fluid entering the cylinder 56 from the space within tubing 2i). When the pressure within the tubing exceeds the pressure within the casing by a predetermined amount, `for example 1,25 p.s.i., the pressure differential causes rod 53 to move down and gate 50 to swing clockwise from the full line position shown. In this alternate or raised position, the indented end of gate 50 receives another ball 28' from bore 26. When fluid Apressure in the tubing is decreased sufficiently, spring 6@ raises rod 53 and the gate swings back, counter-clockwise, to the lowered position shown. In this position the ball at 28a is free to drop by gravity into the space 12a within the casing. Hence it is by a decrease in pressure in the fluid that a ball is released into the fiuid stream with this type of release mechanism. Thus it will be seen that the method of releasing plugging elements to plug openings in the casing using the apparatus illustrated in FIG. 4 is essentially the same as previously described. Although not shown'in FIG. '4, body 25a has one or more fluid passages 42 containing a check valve that opens to permit downward iiow only, as illustrated and described in connection with the embodiment of the invention in FIG. 2.

From the foregoing it will be evident that variations in our method of and apparatus for temporarily plugging .openings in an oil well casing and apparatus for practising that method, may occur to persons skilled in the art without necessarily departing from the spirit and scope of our invention. Since such variations are considered to be included within the scope of the appended claims the foregoing description is considered to be illustrative of, rather than limitative upon the invention as defined by these claims. We claim: 1. The method of temporarily plugging openings in a casing set in a well that comprises:

lowering within the casing a plurality of discrete plugging elements, while externally confining the elements in a compact group, to a position in the vicinity of the openings in the casing; introducing fluid under pressure into said casing to cause the fluid to iiow outwardly through said openings while the elements in said group are isolated from flow of fluid under pressure; transmitting a control impulse through the well to the magazine; separating at least one of the plugging elements from the group and in response to said control impulse releasing the separated element into the iluid stream at a position in the vicinity of but above the elevation of an opening to be plugged to be carried by the stream to the opening to be plugged and seated in said opening. 2. The method of temporarily plugging openings in a casing set in a well that comprises:

lowering within the casing a plurality of discrete plugging elements, while externally coniining the elements in a compact group, to a position in a vicinity of the openingsin the casing; introducing uid under pressure into said casing to cause the uid to flow outwardly through said openings while the elements in said group are isolated from ow of lluid under pressure; transmitting a control impulse through the well to the magazine; separating plugging elements individually from the group and in response to said control impuise releasing the individual elements in succession into the 1? -fluid stream at a position in the vicinity of openings to be plugged, to be carried individually by the lluid stream to the openings to be plugged and seated'in said openings.

3. In apparatus for releasing plugging members into a body of uid in a well, the combination with a tubing string extending down into the well, comprising:

a magazine mounted on the lower end of the tubing string and holding a plurality of plugging elements, the magazine having an outlet for said elements opening into the well space containing the body of fluid and through which outlet elements can pass into said well space;

gate means at the outlet from the magazine controlling passage of elements from the magazine through said outlet into the well space;

means defining a iluid passage separated from the magazine and communicating at the inlet end with the tubing and at the outlet end with the well space;

and fluid actuated gate operating means in said passage connected to said gate and responsive to iluid iiowing through the passage to actuate the gate and release elements from the magazine to pass through said outlet into the well space below the tubing string.

4. The combination as claimed in claim 3 in which the gate operating means includes:

an operating member connected to the gate;

and fluid pressure responsive means also connected to the operating member to move said member and the gate in response to a pressure vdifferential between tluid in the tubing and in the well space.

5. Apparatus for temporarily plugging openings in casing set in a well having a tubing string within the casing, comprising:

a magazine attached to the lower end of the tubing string and containing a plurality of plugging elements;

means at the lower end of the magazine providing a passage between the magazine and the well space through which said elements can pass;

gate means at the lower end f the magazine adapted to control the passage of elements out of the magazme;

and operating means connected to the gate and operable in response to a control impulse transmitted to the operating means through iluid in the well to eiiect v passage of said elements out of the magazine. 6. The method of manipulating plugging elements within a well down which uid is being pumped that includes the steps of lowering in the well a plurality of elements as a group within a container to a position in the vicinity of holes to be plugged by the elements; 4

generating a control impulse at the ground surface;

transmitting the control impulse through lluid in the well to releasing mechanism carried by the container for the group vof elements;

and releasing at least one of saidelements from the group in response to the control impulse received at the releasing mechanism.

7. The method as claimed in claim 6 in which the control impulse is a transient change in uid pressure within the well.

8. The method manipulating plugging elements within a well down whichiluid is being pumped that includes the steps of lowering in the well a plurality of elements as a group within a container to a position in the vicinity of holes to be plugged by the elements;

controlling uid flow down the Well;

and effecting release of elements from the group in response to a change in a characteristic of said controlled Huid ow past the group of elements.

9. Apparatusfor temporarily plugging openings in casing set in a well having a tubing string within the casing comprising: i

a magazine attached to the lower end of the tubing string and containing a plurality of plugging elements, said magazine being located in the vicinity of the openings in the casing to be plugged;

means at the lower end of the magazine providing a ball transmitting passage from the magazine into the casing below the magazine, said means including gate means in the passage at the lower end of the magazine adapted to control the discharge of elements lout of the magazine and through the passage;

and operating means connected to said gate and operable in response to the ow of Iluid from the tubing into the casing and toward the Aopenings to be plugged.

l0. Apparatus according to claim 9 in which the gate means includes a pivotally mounted member having limited vertical travel to discharge the plugging elements one at a time, and the gate operating means includes a gate operating rod connected to the gate and movable in response to a change in pressure differential between the fluid within the tubing and within the casing.

l1. Apparatus for temporarily plugging openings in casing set in a well having a tubing string within the casing, comprising:

a magazine attached to the lower end of the tubing string and containing a plurality of plugging elements, said magazine being located in the vicinity of the openings in the casing to be plugged and open at its lowerend to discharge plugging elements into the casing;

gate means at the open end of the magazine adapted to control the passage of elements out of the magazine; i

a first iluid passage means between the interior and the exterior of the tubing;

a check valve in said passage;

spring means urging the check valve to a closed position, lthe valve opening in response to a predetermined excess of fluid pressure in the tubing;

an operating rod interconnecting the gate means and said check valve, the check valve shifting the gate means in one direction to pass at least one element out of the magazine in response to motion of the check valve to an open position, said spring means returning the gate means to a position holding the `elements in the magazine;

a second fluid passage between the interior and the exterior of the tubing;

and a second check valve located in the second passage opening in response to a higher iluid pressure in the casing than the first mentioned predetermined iluid pressure at which the first mentioned valve opens.

l2. Apparatus for temporarily plugging openings in casing set in a well having a tubing string within the casing, comprising:

a magazine attached to the lower end of the tubing string and containing a plurality of plugging elements, said magazine being located in the vicinity of the openings in the casing to be plugged and open at its lower end to discharge plugging elements into the casing;

gate means at the open end of the magazine adapted to control the passage of elements out of the magazine; Y

apiston exposed to iluid pressure in the tubing;

spring means normally urging the piston to a iirst position, said piston being movable to a second position in response to a predetermined excess of tluid pressure in the tubing over the fluid pressure in the casing, said piston being connected to the gate means and shifting the gate means, in response to said motion of the piston to said second position, to a position in which the gate passes at least one element out of the magazine;

a fluid passage between the interior and the exterior of the tubing;

and a check valve located in the Huid passage opening in response to a higher uid pressure in the casing than the irst mentioned iluid pressure to which the piston responds.

13. In apparatus for releasing plugging members into a body of iluid in a well, the combination comprising:

a magazine holding a plurality of plugging elements, said magazine having an outlet opening to the well space containing the fluid body and through which opening elements can pass into said well space;

means supporting the magazine a substantial distance down the well below the top of the well;

gate means at the outlet from the magazine adapted to control the passage of elements through said outlet from the magazine into the well space;

operating means connected to said gate and responsive 10 to an impulse generated at the top of the Well to operate the gate to discharge at least one element through the passage into the Well space; and means transmitting said impulse from the top of the well down the well to said gate operating means.

14. Apparatus as claimed in claim 3 in which the means transmitting the impulse includes a column of liquid in the well extending between the top of the well and said gate operating means.

References Cited in the le of this patent UNITED STATES PATENTS 23,583 Eilert Nov. 18, 1952 2,634,098 Armentrout Apr. 7, 1953 2,698,582 Vincent Ian. 4, 1955 2,754,910 Derrick et al Iuly 17, 1956 2,790,500 Jones Apr. 30, 1957 2,813,490 ONeal Nov. 19, 1957 3,011,548 Holt Dec. 5, 1961 

8. THE METHOD MANIPULATING PLUGGING ELEMENTS WITHIN A WELL DOWN WHICH FLUID IS BEING PUMPED THAT INCLUDES THE STEPS OF LOWERING IN THE WELL A PLURALITY OF ELEMENTS AS A GROUP WITHIN A CONTAINER TO A POSITION IN THE VICINITY OF HOLES TO BE PLUGGED BY THE ELEMENTS; CONTROLLING FLUID FLOW DOWN THE WELL; AND EFFECTING RELEASE OF ELEMENTS FROM THE GROUP IN RESPONSE TO A CHANGE IN A CHARACTERISTIC OF SAID CONTROLLED FLUID FLOW PAST THE GROUP OF ELEMENTS.
 9. APPARATUS FOR TEMPORARILY PLUGGING OPENINGS IN CASING SET IN A WELL HAVING A TUBING STRING WITHIN THE CASING COMPRISING: A MAGAZINE ATTACHED TO THE LOWER END OF THE TUBING STRING AND CONTAINING A PLURALITY OF PLUGGING ELEMENTS, SAID MAGAZINE BEING LOCATED IN THE VICINITY OF THE OPENINGS IN THE CASING TO BE PLUGGED; MEANS AT THE LOWER END OF THE MAGAZINE PROVIDING A BALL TRANSMITTING PASSAGE FROM THE MAGAZINE INTO THE CASING BELOW THE MAGAZINE, SAID MEANS INCLUDING GATE MEANS IN THE PASSAGE AT THE LOWER END OF THE MAGAZINE ADAPTED TO CONTROL THE DISCHARGE OF ELEMENTS OUT OF THE MAGAZINE AND THROUGH THE PASSAGE; AND OPERATING MEANS CONNECTED TO SAID GATE AND OPERABLE IN RESPONSE TO THE FLOW OF FLUID FROM THE TUBING INTO THE CASING AND TOWARD THE OPENINGS TO BE PLUGGED. 